Provided is a method of forming a nonvolatile memory device. The method may include alternatingly stacking n number of dielectric layers and n number of conductive layers on a substrate, forming a non-photosensitive pattern on the alternatingly stacked dielectric layers and conductive layers, etching the i-th conductive layer and i-th dielectric (2≦i≦n, i is a natural number indicating a stacking order of the conductive layers and the dielectric layers) by using the non-photosensitive pattern as an etch mask, laterally etching a sidewall of the non-photosensitive pattern and etching the i-th conductive layer, (i−1)-th conductive layer, i-th dielectric layer and (i−1)-th dielectric layer by using the etched non-photosensitive pattern as an etch mask.